The present invention relates to self-adhesive tiles and to a process for the manufacture thereof.
There are various known methods of fixing ceramic tiles to walls and other surfaces. The oldest method is to set the tiles in a bed of wet sand and cement mix, and today this method is widely practised using so-called "thin bed cements". These beds usually have a thickness of between 2 and 5 mm and can be prepared using a water-based adhesive containing cement mix, a water-based thick, filled rubber adhesive or an adhesive based on a filled polyvinyl acetate or other polymer emulsion.
Alternatively, the tiles are "buttered" on the back with a layer of wet adhesive of the above type to the required thickness or thick lines or spots of adhesive are applied to the back of the tiles (termed "spot fixing"). When using this alternative method, it is essential that the wet adhesive should be applied as a whole or partial coating having a thickness of at least 1 mm, usually 1 to 5 mm, in order that protrusions and indentations in the surface to be tiled and/or any slight distortions in the tiles themselves can be accommodated.
It is also of importance for good tiling that the adhesive should remain in an unset condition for a reasonable period of time, for example, five to ten minutes or even longer, so that after a number of tiles have been positioned on the surface, it remains possible to move the tiles at least fractionally to correct discrepancies resulting from the unevenness of the surface, distortions in the surface of the tiles, and size differences in the tiles, thereby to avoid staggered grout lines.
It is also known to make self-adhesive ceramic tiles where the tiles are provided on the back surface with a whole or partial coating of a pressure-sensitive adhesive. When a pressure-sensitive adhesive is used alone in this manner the coating usually has a thickness of 0.2 mm or more, and when thinner coatings are used a compressible underlay, e.g. expanded polystyrene or netting, is put on the back of the tiles to take up unevenness in the surface to be tiled. The disadvantage of using this kind of tile (dry tiling) is that the tiles, once positioned on a surface, are fixed immediately and cannot easily be moved to correct discrepancies as mentioned above.
Flexible tiles provided with a solvent-activatable adhesive coating are described in U.S. Pat. No. 3,442,730. The solvent-activatable coating is based on a polymeric material which is applied as a very thin layer of from 0.004 to 0.006 inches to a surface of a flexible tile. A very thin coating of this type would be of no use for application to rigid tiles, since it would not accommodate any unevenness or irregularity in the surface to be tiled.
The adhesive coating is activatable by a suitable solvent such as an alcohol admixed with a small amount of water. The coating is not, however, activatable by means of water alone as the solvent.
Tiles provided with their own coating of a water-soluble re-moistenable adhesive have not, up to now, been used or made for the purpose of tiling because the usual tile adhesive or tile cements when applied to tiles in wet paste form in a suitable thickness, and then dried, cannot be easily re-activated to their original paste form. On drying a skin forms on a coating of adhesive of suitable thickness which prevents water from penetrating the coating so that it is difficult to re-activate the adhesive within a reasonable period of time to provide a suitably soft adhesive paste which will spread easily when the tile is applied to a surface. In any case an adhesive of this type would remain water sensitive and therefore unsuited to service in bathrooms and showers. Hydraulic materials when applied in water cannot be re-activated at all after setting and drying.
I have now developed a process for the manufacture of self-adhesive ceramic or other rigid tiles having a dry hydraulically active tile composition adhered to a face thereof, whereby on immersion or dipping of the tiles in water the dry hydraulically active tile composition absorbs enough water to be converted into a paste having adequate adhesive and hydraulic properties for the tiles to be fixed to the surface to be tiled.